Automatic draft control



Dec. 21, 1937. AN ER ON 2,102,873

AUTOMATIC DRAFT CONTROL Filed Jan. 2, 1956 Fig ll C/Oy for? 6. Anderson[/7 7/6 nzor A Ziorney.

Patented Dec. 21, 1937 UNITED STATES AUTOMATIC DRAFT CONTROL Clayton G.Anderson, Portland, Oreg., assignor of forty-nine percent to Charles P.Dougherty,

Portland, Oreg.

Application January 2, 1936. Serial No. 57,090

5 Claims.

This invention relates to thermostatic draft control for furnaces andparticularly for oil burning furnaces of the intermittent type, such asare used in residences, though it is generally useful.

In furnaces of the type mentioned, conditions prevail that are differentfrom furnaces in continuous use. They do not run steadily since nostructure has yet been developed that will vary the heat production to apoint that will exactly meet requirements, hence they are made as an onand off control device, requiring a fall of temperature of a few degreesin space to be heated to start the oil burner, which then heats to a fewdegrees above the median temperature, when a thermostat acts tointerrupt its action. This is repeated from time to time and during theoff period the combustion chamber cools to a point well below theignition point of the fuel used, resulting in poor combustion of theatomized fuel air mixture'when it is injected into the comparativelycool furnace, during the first short interval after the burner ignitesfor a fire period.

To avoid. disagreeable odors during that period it is necessary that anadequate draft be provided with connections to a chimney, to carry offthe odors of incompletely burned oil vapor or spray that has been cooledbelow burning temperature by contact with the comparatively cool wallsof the furnace interior.

Immediately the furnace temperature rises to a point where no odors willdevelop it is economical to immediately check the draft automatical- 1y,so that an excessive amount of heat will not be carried up the chimney.

The object of my invention is to meet the conditions named with astructure that is at once eifective, of low cost and not liable to getout of order. These and other objects that will be at once apparentconstitute the purpose of the present invention, the base purpose beingsatisfactory operation with economy.

Drawing accompanies and forms a part of this specification illustratinga form thereof that has proved highly satisfactory from every viewpointof the conditions named and will be herein explained as the preferredform of the invention though I do not wish to limit myself except by theappended claims. 7

In the drawing,-- 7

Fig. I is a section of a smoke pipe assumed to be in position between afurnace and a chimney, being taken on the line 1-1 of Fig. II;

Fig, II is also a sectional view of the same structure shown in Fig. Itaken on the line II-II of Fig. I. For convenience in attaching, thedevice is shown as a clamp-like structure capable of being attached toan existing pipe without much dis- 5 turbance of the pipe as originallyinstalled.

I represents the smoke pipe and an opening 2 is made in the wallthereof;v that registers with the chamber 3 of the draft controlapparatus now to be described. 9

The draft control apparatus is shown in the form of a clamp thatsurrounds the pipe I and is made in'two halves, a band portion 4,provided with a flange 5 arranged to mate with a corresponding fiange 6of the structure proper indicated in general by the numeral I.

Walls Ia and a closure 8 define a chamber 3 alongside the pipe I. Withinthe chamber 3 is a staff 9 that is rotatively mounted in openings lb inthe walls Ia as shown in Fig. II. 20

A coil spring III which may be of any preferred metal, steel forexample, surrounds the staff 9 and serves as a thermostat. One end ofthe spring is made rigid with the relatively fixed wall of the closure 8or at 8a or any convenient point and the other end is made rigid withthe staff 9 at 9 I. Both the sensitivity and the overall movement of thespring Ill are a function of its length and the expansion coefficient ofthe material of construction. If made of brass it need be only 30 abouthalf as long as when made of ferrous metal.

Changes of temperature within the chamber 3 affect the spring I0 andcause it to coil up and .uncoil according to temperature change. 35

Rotative motion of the staff 9 is communicated to a damper I2 placed inthe pipe I in the well known manner by means of transmissiondiagrammatically indicated by the levers I3, I4 and I5 which areoperatively connected to the staff 9 at one end of the train and to thedamper pivot I2aI at the other end.- Obviously temperature changes ofthe pipe I are immediately communicated to the chamber 3 and the springIII to move the damper I2 to control the pipe I in the well known mannerof dampers so disposed.

Made rigid with the lever I3 is the bellcrank lever I3a. to which ispivotally connected the rod I5. The rod I5 is provided with the collarI5a and runs loosely through the lug I8 of the check draft I9, with lostmotion of sufficient degree that the check-draft will not open until thedamper I2 is nearly in its extreme position tending to obstruct the pipeI, when it Will'open very abruptly. A deflector plate 25 is positionedto 55 protect the spring ID from the rush of incoming cold air when thecheck draft I9 is open. This has been omitted from Fig. II for clarityin the drawing. A leaf spring 26 keeps the check draft normally closed.

The check draft, controlled by the lost motion device so that it willopen abruptly by the last end movement of the staff 9 and close asabruptly when the shaft 9 reverses, is an important point in thestructure.

Having thus fully disclosed the nature of this invention, and a mannerof constructing the same, what I desire to secure by Letters Patent,is,-

1. A self-contained draft control apparatus for attachment to a furnacepipe, comprising a frame to surround a pipe, a pipe damper therein, athermostat chamber within said frame, a thermostat mounted in saidchamber, a check draft positioned to admit outside air above the damperand transmission means interconnecting the thermostat, the damper andthe check draft for constant cooperative movement of the damper with thethermostat and a lost motion in said transmission to effect intermittentmovement of the check draft at a predetermined high temperature.

2. Draft control means for a furnace pipe comprising in combination aclamp for rigidly surrounding a portion of the exterior of a smoke pipe,pipe damper, check draft and thermostat mountings formed within saidclamp member, a pipe damper, a check draft and a thermostat in saidmountings and transmissions between the damper, the check draft and thethermostat, said transmissions being arranged to abruptly move the checkdraft when the damper is in nearly closed position.

3. Draft control means for a furnace pipe comprising a clamp adapted forrigid attachment externally of a pipe to comprise a portion of the same,a pipe damper, a check draft and a thermostat contained in said clampand mounted for movement therein, transmissions between the thermostatand the pipe damper that are arranged to transmit proportionate movementto said damper, a transmission between said thermostat and said checkdraft and a lost motion device in said last named transmission that isarranged to abruptly operate the check draft when the damper issubstantially closed.

4. Draft control apparatus comprising a frame member for rigid insertionin a flue as a portion thereof, an opening in said frame, a check draftpositioned to control said opening, a damper positioned in the frame tocontrol the flue, a thermostat that is effective to control the damperaccording to temperature of gases passing through the flue andtransmissions between the thermostat and the check draft that areeffective to operate said check draft abruptly at a predetermined hightemperature.

5. Flue draft control apparatus comprising a frame member adapted forinsertion in a smoke pipe to form a part thereof that is provided with aside opening, a check draft member mounted for movement to control saidopening, a damper mounted for movement to control the smoke pipe and athermostat device that is effective to move the damper to close thesmoke pipe as the temperature therein rises and to abruptly open thecheck draft when the damper has been moved to nearly close the pipe.

CLAYTON G. ANDERSON.

